{No problems for White here: there are a couple of points in the opening you
could have another look at.} 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 d6 5. d4 exd4
{So far, so good!} 6. Nxd4 ({The idea of c3 is to take over the centre, and
you can do that with a gain of time here after} 6. cxd4 Bb6 7. Nc3 $16) 6...

You have to be able to make a decent start in a game of chess, or you risk being blown away by your opponent's better development. Knowing a few openings in a bit of detail is some insurance against traps and ideas that you haven't seen before.

So, here are some variations in common openings that you can -- and should -- learn. At each turn, try and learn not just what is the right move(s) but why that move is preferred.